Is your iPad not charging over USB with your computer? Here’s why: It’s a not a high power USB port. Yes, that’s why it’s not charging. If your computer is 2 or 3 years old chances are that your computer doesn’t have a high power USB port. If you have a computer that’s 1 year old or less, there’s still a good chance it doesn’t have a high power USB port. Now, a 2009 MacBook Pro (13-inch) does have a high power USB port. Also, that’s why Apple included a different power adapter with the iPad.